I use the tone generator in my Peterson V-SAM to test the
accuracy on some electronic tuners.

Most essential is the
precision with which the tuner can display the result! Even
if the tuner can measure with high precision, it is not shure it is able
to present the result with the same precision!

Tuners have an interval where they show that the note
is in tune! I have measured how wide this interval is. If an interval is 6 cent
wide, it means -3 cent below and +3 cent above the correct pitch. Quite
often the approved interval is not centered at the correct pitch.

10 cent

Cherub Guitar MatePrecision not
specified in the manual.

6 cent

KORG DT-3The manual says the precision
is ±1 cent.

6 cent

IntellitouchIn the higher octaves the interval was centered
about 2 cents sharp.
The manual says the precision is "better than one cent".